1. Field of the Invention
The present invention relates to an apparatus and method for containment of waterborne contaminates. More particularly, the present invention relates to an oil spill containment boom having a substantially vertical skirt section extending downwardly into the body of water, which skirt section can be overlapped and secured together so as to prevent the escape of the captured oil.
2. Background Art
The harmful effects of a wide variety of waterborne contaminates, both to the natural environment and to the human population, are well known. While any number of substances may form harmful waterborne contaminates, a particularly common and egregious example is oil spills. Oil spills typically may originate from either naturally occurring or accidental man-made hydrocarbon leaks. Accidental oil spills originate from a wide variety of sources, including, by way of example: offshore platforms, oil transfer facilities, shoreline refineries, and oil tankers. Accordingly, such accidental spills may take place in either open water or coastal areas. Typically, oil spills in open ocean areas take the form of thin, isolated slicks floating on the surface of deep water. Oil spills in coastal areas, however, may form slicks in shallow water bays, estuaries, rivers, etc., which are subject to significant current and tidal forces.
Many oil spill booms for retaining or cleaning up such oil spills are well known to those skilled in the art. Traditionally, such booms have taken the form of elongate floating barriers having a shallow skirt section which extends downwardly into the water. Such booms are traditionally towed in a "U"-shaped configuration by two vessels so as to collect the floating oil between the open ends of the boom. One such typical boom is that disclosed in U.S. Pat. No. 3,852,965 (Issued Dec. 10, 1974 to Rudd). Rudd discloses a boom having a floating surface barrier with a relatively short (approximately 4 foot) depending curtain. The lower-most portion of the curtain is open for the passage of water. A tow line is attached to the bottom of the skirt for pulling the lower portion of the curtain in advance of the floating barrier. The boom is adapted to be towed behind two vessels. As the boom is towed through the water, the floating material to be collected accumulates in front of the floating member and skirt and the excess water flows through the open portion of the curtain. Another traditional "U"-shaped floating boom is disclosed in U.S. Pat. No. 3,922,862 (Issued Dec. 2, 1975 to Vidilles). Vidilles discloses a boom having an upper float element, below which is a relatively shallow skirt. The skirt tapers from having a deeper section at the mid-point of the boom towards the surface at either end of the boom. Accordingly, the skirt is intended to entrain water and pollutants only near the vertex of the "U", so as to avoid entraining additional water near the leading edges of the "U". A tow chain is attached along the lower edge of the skirt so as to provide ballast which maintains the skirt at its proper depth. Yet another such skimming boom is disclosed in U.S. Pat. No. 3,686,870 (Issued Aug. 29, 1972 to Blomberg). Blomberg discloses a boom having a stress relieving rope connected at points situated along its length so that the total stress exercised by the water resistance when the boom is towed through the body of water will be taken up by the stress relieving rope, whereby each section of the boom is only subjected to the water resistance stress actuating upon that individual section. The boom is provided with floats along the upper edge of the skirt, and sinking weights along the lower edge of the skirt. The skirt is attached to the stress relieving rope by means of tethers, such as supporting wires. The main purpose of the stress relieving rope described by Blomberg appears to be to relieve the towing stress exerted on each individual panel or section of the boom. Although Blomberg states that the stress relieving rope can be used to haul in each individual section separately if the boom is going to be brought home or pursed around leaked out oil, Blomberg does not appear to teach or suggest that the boom may be used to completely enclose or confine an oil slick.
While such conventional "U"-shaped booms may prove helpful in cleaning up oil slicks, they typically exhibit a number of drawbacks and disadvantages. For example, such "U"-shaped booms typically require the services of two tugs, boats, or other watercraft to tow them through the water. Typically, a watercraft is attached to either end of the "U", and the pair of craft proceed on parallel courses so as to maintain the boom in its proper orientation. The craft maneuver the "U"-shaped boom through contaminated areas so as to collect or "sweep up " floating oil from the surface of the water. It is readily apparent that each additional craft required for an operation significantly increases total costs. Furthermore, in the event of a catastrophic spill, it is highly likely that there will be a shortage of available clean-up craft. Accordingly, there is need for an apparatus method which would permit the clean-up of spilled contaminants using fewer craft.
Another disadvantage of the traditional "U"-shaped skimmer booms is that they require continued forward motion of the craft to keep the oil or other contaminates contained within the vertex of the "U" shaped collection area. Unless a harbor skimmer or other oil removal means is readily available to remove the collected materials once the forward movement of the towing craft has ceased, the spill will immediately commence spreading again over the surface of the water. Such harbor skimmers or other removal means are typically very expensive, and would also likely be in very short supply in the event of a major spill. Furthermore, since only the forward motion of the boom through the water serves to collect and compress the oil into a compact mass within the boom, once the motion of the boom stops, even if collection craft are available, the slick will immediately begin to spread out as a thin film over the surface of the water. Collection of such a thin slick is typically accomplished by means of a conventional harbor skimmer, and is both time consuming and highly inefficient. Such conventional harbor skimmers tend to collect a great deal of water with the oil, and their collection capacity is soon reached. It would be much more efficient to collect and maintain the oil slick in a compact, fairly thick mass at the surface of the water from which it could be efficiently pumped or drawn by a collection craft. Accordingly, there is a need for an apparatus and method for collecting and storing floating contaminates such as oil in a relatively compact mass until a removal craft becomes available.
Still further, because traditional "U"-shaped skimmer booms must be drawn through the water in order to collect the oil slick, significant difficulties with spillage of the collected oil over and under the booms has been encountered in the practice of such techniques. These difficulties are aggravated by heavy weather, since the forward motion of the boom though the body of water creates additional turbulence which adds to the ambient turbulence of the wave action. Such booms can also easily be damaged by floating debris such as logs, or by fixed objects such as rocks; in the event that the towing craft maneuver to avoid such hazards, significant portions of the surface of the body of water may be left unswept. Accordingly, there is a need for a technique by which oil slicks and other contaminates floating on a body of water can be captured without sweeping through the water with a boom.